<pre>
#if 视为false的情况：
    ''
    false
    null
    0
    [](*)
#each 空数组视为false
    
</pre>

<hr>bool<br>

{{#if bool}}
true:bool
{{else}}
false
{{/if}}

<hr>string<br>
{{#if string}}
string
{{else}}
空字符串
{{/if}}


<hr>null<br>
{{#if NULL}}
true:null
{{else}}
null
{{/if}}

<hr>0<br>
{{#if number}}
true:0
{{else}}
0
{{/if}}


<hr>emptyArray-if<br>
{{#if emptyArray}}
emptyArray
{{else}}
[]
{{/if}}

<hr>emptyArray-each<br>
{{#each emptyArray}}
each:{{.}}<br>
{{else}}
[]
{{/each}}

<hr>emptyObject-if<br>
{{#if emptyObject}}
true:emptyObject
{{else}}
{}
{{/if}}